/*-
 * Copyright (c) 2014 The University of Oslo
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "cryb/impl.h"

#include <stdint.h>
#include <string.h>

#include <cryb/hash.h>

/*
 * Implementation of the hash function described in Pearson, Peter
 * K. (June 1990), "Fast Hashing of Variable-Length Text Strings",
 * Communications of the ACM 33 (6): 677, doi:10.1145/78973.78978
 */

static const uint8_t T[256] = {
	0x01,	0x57,	0x31,	0x0c,	0xb0,	0xb2,	0x66,	0xa6,
	0x79,	0xc1,	0x06,	0x54,	0xf9,	0xe6,	0x2c,	0xa3,
	0x0e,	0xc5,	0xd5,	0xb5,	0xa1,	0x55,	0xda,	0x50,
	0x40,	0xef,	0x18,	0xe2,	0xec,	0x8e,	0x26,	0xc8,
	0x6e,	0xb1,	0x68,	0x67,	0x8d,	0xfd,	0xff,	0x32,
	0x4d,	0x65,	0x51,	0x12,	0x2d,	0x60,	0x1f,	0xde,
	0x19,	0x6b,	0xbe,	0x46,	0x56,	0xed,	0xf0,	0x22,
	0x48,	0xf2,	0x14,	0xd6,	0xf4,	0xe3,	0x95,	0xeb,
	0x61,	0xea,	0x39,	0x16,	0x3c,	0xfa,	0x52,	0xaf,
	0xd0,	0x05,	0x7f,	0xc7,	0x6f,	0x3e,	0x87,	0xf8,
	0xae,	0xa9,	0xd3,	0x3a,	0x42,	0x9a,	0x6a,	0xc3,
	0xf5,	0xab,	0x11,	0xbb,	0xb6,	0xb3,	0x00,	0xf3,
	0x84,	0x38,	0x94,	0x4b,	0x80,	0x85,	0x9e,	0x64,
	0x82,	0x7e,	0x5b,	0x0d,	0x99,	0xf6,	0xd8,	0xdb,
	0x77,	0x44,	0xdf,	0x4e,	0x53,	0x58,	0xc9,	0x63,
	0x7a,	0x0b,	0x5c,	0x20,	0x88,	0x72,	0x34,	0x0a,
	0x8a,	0x1e,	0x30,	0xb7,	0x9c,	0x23,	0x3d,	0x1a,
	0x8f,	0x4a,	0xfb,	0x5e,	0x81,	0xa2,	0x3f,	0x98,
	0xaa,	0x07,	0x73,	0xa7,	0xf1,	0xce,	0x03,	0x96,
	0x37,	0x3b,	0x97,	0xdc,	0x5a,	0x35,	0x17,	0x83,
	0x7d,	0xad,	0x0f,	0xee,	0x4f,	0x5f,	0x59,	0x10,
	0x69,	0x89,	0xe1,	0xe0,	0xd9,	0xa0,	0x25,	0x7b,
	0x76,	0x49,	0x02,	0x9d,	0x2e,	0x74,	0x09,	0x91,
	0x86,	0xe4,	0xcf,	0xd4,	0xca,	0xd7,	0x45,	0xe5,
	0x1b,	0xbc,	0x43,	0x7c,	0xa8,	0xfc,	0x2a,	0x04,
	0x1d,	0x6c,	0x15,	0xf7,	0x13,	0xcd,	0x27,	0xcb,
	0xe9,	0x28,	0xba,	0x93,	0xc6,	0xc0,	0x9b,	0x21,
	0xa4,	0xbf,	0x62,	0xcc,	0xa5,	0xb4,	0x75,	0x4c,
	0x8c,	0x24,	0xd2,	0xac,	0x29,	0x36,	0x9f,	0x08,
	0xb9,	0xe8,	0x71,	0xc4,	0xe7,	0x2f,	0x92,	0x78,
	0x33,	0x41,	0x1c,	0x90,	0xfe,	0xdd,	0x5d,	0xbd,
	0xc2,	0x8b,	0x70,	0x2b,	0x47,	0x6d,	0xb8,	0xd1,
};

uint8_t
pearson_hash(const void *data, size_t len)
{
	const uint8_t *p;
	uint8_t h;

	for (p = data, h = 0; len > 0; ++p, --len)
		h = T[h ^ *p];
	return (h);
}

uint8_t
pearson_hash_str(const char *str)
{
	uint8_t h;

	for (h = 0; *str != '\0'; ++str)
		h = T[h ^ (uint8_t)*str];
	return (h);
}